1. Field of the Invention
The present invention generally relates to data recording/reproduction apparatus for optical disks, which apparatus each include an optical pickup which can record, reproduce, or erase data by projecting a laser beam into a spot on an optical disk such as a compact disk (CD) or a digital versatile disk (DVD), and more particularly to a data recording/reproduction apparatus which can adjust a tilt and a height of the optical pickup with respect to an optical disk.
2. Description of the Related Art
As a recent trend, optical disks have been shifting from CDs to DVDs, each of which includes a storage capacity approximately seven times as large as that of a CD. To comply with the increase in the storage capacity, it is required of an optical pickup to reduce a diameter of a beam spot formed on an optical disk by a laser beam projection. Therefore, a wavelength of a laser beam projected from a light source of a semiconductor laser is reduced, and a numerical aperture (NA) of an objective lens is increased, causing a tilt of the objective lens with respect to the optical disk to become an important point.
In other words, when the objective lens is tilted with respect to the optical disk, a coma is caused in the beam spot. The larger the numerical aperture, the more easily the coma is caused. The coma deteriorates performance of the beam spot, thus worsening jitter (instability of information data in its time-axial direction) at a time of recording or reproduction.
Therefore, a common DVD drive adjusts a tilt angle formed between an optical disk and an objective lens. With respect to means for such an adjustment, a large number of technologies have already been disclosed in patent applications. For example, Japanese patent application Nos. 10-69650, 10-112122, and 10-208372 each disclose a recording/reproduction apparatus which mounts a spindle motor on a plate whose tilt with respect to a base body is adjustable so as to adjust a tilt angle formed between an optical disk and an objective lens.
Further, Japanese patent application Nos. 11-25466 and 11-149724 each disclose a recording/reproduction apparatus which adjusts a tilt of a guide shaft which guides movements of an optical pickup in radial directions of an optical disk.
That is, these prior art technologies are roughly divided into two types: a first type which adjusts a spindle motor on which an optical disk is placed and a second type which adjusts an optical pickup which includes an objective lens.
With respect to the first type of prior art technologies, rigidity for supporting the spindle motor is reduced because the spindle motor is not directly fixed to the base body. Therefore, when the optical disk is rotated, strong vibrations are caused by rotational movements of the spindle motor. A DVD drive is required to record/reproduce data on/from a CD as well, and a rotational speed thereof has increased lately to reach a maximum of 10,000 rpm. In the case of a spindle motor with such a high rotational speed, vibrations are generated in an optical disk or an optical pickup without high rigidity for supporting the spindle motor, thus causing instabilities in recording/reproduction operations. If a CD or a DVD has an eccentricity, strong vibrations are caused. In such a case, if rigidity for supporting the spindle motor is low, great vibrations are transmitted to the optical disk or the optical pickup.
Further, the optical disk is tilted by tilt-adjusting the spindle motor. Therefore, in the case of using a cartridge housing an optical disk, the optical disk may touch the inner wall of the cartridge by being tilt-adjusted in the cartridge.
With respect to the second type of prior art technologies, the guide shaft, which is a seek-type guide unit for actuating the optical pickup in radial directions of an optical disk (or for an access operation of the optical pickup), is tilted. However, since guide rails are not directly fixed to a base body, rigidity for supporting the optical pickup is reduced. Therefore, strong vibrations are caused during a high-speed access operation of the optical pickup.